1. Field of the Invention
The invention relates to an electronic apparatus and more particularly relates to an internal voltage generating apparatus.
2. Description of Related Art
With the advances in semiconductor technology, power lines inside chips become longer and more slender, which causes a serious IR drop problem that affects a normal operation of the electronic apparatus. For example, such a problem may cause memory data loss for storage devices and cause non-uniform brightness of the display panel for display devices.
Take a low power double data rate (LPDDR) dynamic random access memory (DRAM) as an example, the external voltage supply is 1.8V only, and the internal voltage of the chip is all generated through a regulator. Take the internal voltage generating apparatus shown in FIG. 1 for example, a power voltage VDD (1.8V) provided by a power pad P0 drops to voltage VDD_local (1.6V) due to the IR drop of the internal power line. However, through the regulator composed of a transistor Q1 and an operational amplifier OP0, the stable internal voltage VINT (1.2V) can still be generated.
For a LPDDR2 dynamic random access memory (DRAM), because the external voltage has an additional 1.2V, no additional regulator is required for IR drop, which is more convenient, but it becomes more difficult to eliminate the IR drop of the internal local power. Take the internal voltage generating apparatus of FIG. 2 for example, although the apparatus has dual-power supply (wherein a power pad PA provides a power voltage VDDA and a power pad PB provides another power voltage VDDB (1.2V)), the IR drop effect still causes the internal voltage VINT provided by the power voltage VDDB to drop to 1.0V and results in an abnormal operation of the electronic apparatus.